1. Field of the Invention
The present invention relates to an organic electro-luminescent device of emitting light by converting electric energy into light.
2. Description of the Related Art
An organic electroluminescent device is being aggressively studied and developed because light emission of high brightness can be obtained by low-voltage driving. The organic electroluminescent device has an organic layer between a pair of electrodes, and this is a device where an electron injected from a cathode and a hole injected from an anode are recombined in the organic layer and the energy of an exciton produced is utilized for light emission.
In recent years, the devices are becoming highly efficient by the use of a phosphorescent material. There have been disclosed inventions related to a phosphorescent device using an iridium complex, a platinum complex (see, U.S. Pat. No. 6,303,238 and International Publication 00/57676, pamphlet) or the like as the phosphorescent material, but a device satisfying both high efficiency and high durability has not yet been developed.
Also, inventions related to an organic EL device using a polyarylene material as a high-durability material have been disclosed (see, for example, JP-A-2002-356449 (the term “JP-A” as used herein means an “unexamined published Japanese patent application”)). However, the materials used therein have a condensed ring or a long conjugate system and all are low in the lowest excited triplet level (T1 level) of molecule and when used for a phosphorescent device, such a material quenches the light emitted from the phosphorescent material to decrease the light emission efficiency. This is prominent in the emission of light at a short wavelength, and serious quenching of light emission occurs particularly on use for a blue phosphorescent device.